Fix rubocop warnings

app/models/champ.rb

@@ -153,9 +153,9 @@ class Champ < ActiveRecord::Base
         nil
       end
       self.value = date
-    elsif /^\d{2}\/\d{2}\/\d{4}\s\d{2}:\d{2}$/ =~ value # old browsers can send with dd/mm/yyyy hh:mm format
+    elsif /^\d{2}\/\d{2}\/\d{4}\s\d{2}:\d{2}$/.match?(value) # old browsers can send with dd/mm/yyyy hh:mm format
       self.value = DateTime.parse(value, "%d/%m/%Y %H:%M").strftime("%Y-%m-%d %H:%M")
-    elsif !(/^\d{4}-\d{2}-\d{2}\s\d{2}:\d{2}$/ =~ value) # a datetime not correctly formatted should not be stored
+    elsif !(/^\d{4}-\d{2}-\d{2}\s\d{2}:\d{2}$/.match?(value)) # a datetime not correctly formatted should not be stored
       self.value = nil
     end
   end